White blood cell count

Platelets

Platelet level is the number of platelets or thrombocytes in a given volume of whole blood. Both increased and decreased levels can point to abnormal conditions of excess clotting or bleeding.

Variations In The Test Results

In a hospital setting, it is important to avoid taking blood from the same side as an infusion in order to avoid hemodilution. It should be taken into consideration that some samples that were difficult to obtain, e.g., lengthy venipuncture using a narrow gauge needle, such as a small butterfly, may result in abnormalities due to cell lysis or clotting.

CBC in trauma patients may sometimes be misleading. It presents normal initial levels of hemoglobin which do not exclude a significant hemorrhage. Patient’s hemoglobin value is not a real-time indicator of his or hers intravascular blood volume, and it takes quite some time (minutes-hours) before hemoglobin value reflects the degree of blood loss in trauma patients accurately. Following the trend of serial hemoglobin measurements, every 15 to 30 minutes can provide useful information regarding ongoing blood loss.

In trauma patients elevated white blood cell can often be found, but this occurrence is unlikely due to infection. WBC is elevated due to demargination of WBCs during the stress response.

The physician should look for a “left shift” which indicates the presence of immature forms in the peripheral circulation (bands). Usually, this represents an infectious state.

Decreased WBC

Infection (overwhelming sepsis or viral),

Underlying hematopoietic disease (aplastic anemia, agranulocytosis)

Immunosuppression,

Medications (antibiotics, chemotherapeutic agents)

Patient presenting with neutropenia is at risk of infections from common and opportunistic organisms.

Decreased HCT

Blood loss

Hemolysis

Long-standing anemia

Pregnancy

If suspecting acute loss, the physician should look for schistocytes on the peripheral blood smear. Long-standing anemia can be evaluated by the RBC indices. Administration of fluids in hypovolemic patients or trauma resuscitation will cause a decreased HCT.

Increased HCT

Hemoconcentrated states (dehydration, burns, diarrhea)

High altitude,

Exercise,

Polycythemia Vera

Chronic obstructive lung disease

Decreased Hb

Iron deficiency, vitamin deficiencies, e.g., vitamin B12

Bleeding,

Kidney disease

Inflammatory disorders (rheumatoid arthritis or infections)

Hemolysis (accelerated loss of red blood cells through destruction)

Inherited hemoglobin defects (thalassemia or sickle cell anemia)

Cirrhosis of the liver

Bone marrow failure and cancers that affect the bone marrow

Causes of increased Hb are similar to HCT.

Increased platelet count

Myeloproliferative diseases

Malignancy

Infection

Recent surgery (splenectomy)

Chronic inflammation (i.e., irritable bowel syndrome)

Trauma (massive hemorrhage, thrombus)

Secondary to iron deficiency anemia or hemolytic anemia

In thrombocytosis, there is an excess of platelets (more than 1 million), but they are usually large and nonfunctioning.

Other: menses, poor nutritional states such as iron, folate, and vitamin B12 deficiencies.

Hints And Pitfalls

Patients with serious infections may have completely normal, or even low WBC counts. Overreliance on normal WBC counts in the setting of acute infections may lead to misdiagnosis and delays in patient care.

Toxic granulations, Döhle Bodies, and cytoplasmic vacuolization are remnants of phagocytosis found in neutrophils. These are indicative of more serious bacterial infections.

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